Brain Cat appears as a small cat-like doll with white fur that stands perfectly upright. His head is seemingly protected by a yellow helmet with an ornamental design on the top; it perfectly covers his pointy ears. Brain Cat wears an orange suit that covers most of his body; it has a white collar and a large black bow on the front. Prodding out of the back of his orange shorts is his white tail, which is splashed with black on the triangular tip. His paws are the most cat-like feature about him as his feet are merely ovals with a yellow capping that matches his helmet. Brain Cat has a small, toothy smile and beady red eyes that rest in black sockets.
After Ripper lost control of his body, he talked with Kiri via the Brain Cat doll. He told Kiri that Tōya Kagari is the “bad guy”, and if Kiri defeats him, he will regain his memories, and the Brain Cat will turn into a human. After Kiri attacked Tōya, Ripper regained control of his body and declared that now he is “Freaks”. He was defeated by Tōya and Es, and Kiri was later seen in a hospital with a panda plushie as a replacement for Brain Cat.
Only Kiri could hear the Brain Cat’s voice.
- Brain Cat’s gender is listed as “male (?)” while his age is listed as “?” in released media.